Witnesses and security officials say at least 12 people have been critically injured when a gunman opened fire outside a school in Nigeria’s violence-plagued northeastern state of Yobe.

Multiple students at the College of Administrative and Business Studies (CABS) in the city of Potiskum, situated about 575 kilometers (350 miles) northeast of the capital, Abuja, said the gunman arrived at around 8 a.m. local time (0700 GMT) on Friday, and opened fire at the school gate.

They added that the assailant with explosives strapped to his body, detonated the explosives when he ran out of munitions. However, the explosion resulted in no other casualties.

“We had just started a class when we heard gunshots coming from the direction of the gates and we instantly realized we were under attack which made us rush out of the class,” student Tijjani Musa said.

Mustapha Umar, another student, said the attacker managed to pass through the gates amid the bedlam that broke out after the shootout.

He added the gunman “was chased by a group of students who were frantically trying to subdue him.”

“When he ran out of ammunition he detonated the explosives under his robe, killing himself but no one from the crowd,” Umar noted.

“We have evacuated 12 people with serious gunshot wounds to hospital from the scene of the shooting attack,” said a police officer, who requested anonymity.

There was no immediate claim of responsibility for the act of violence, but Potiskum has on numerous occasions borne the brunt of similar militant attacks carried out by Boko Haram Takfiri terrorists.

Last November, at least 58 people were killed and another 117 injured when a bomber passed unnoticed at the Government Technical Science College in the city to detonate the explosives as students had gathered for an assembly.

Boko Haram says its goal is to overthrow the Nigerian government. It has claimed responsibility for a number of deadly shooting attacks and bombings in various parts of the country since the beginning of its militancy in 2009, which has so far left about 15,000 people dead and displaced about 1.5 million.